Joint for abrasive belts or bands



y 27, 1948- w. BQSUMMERS ETAL.

JOINT FOR ABRASIVE BELTS 0R BANDS Filed June 18, 1947 .Ezveniors Mum/vB. Sumvses Mum/v A. 60255 flffi nay abrasive belts or bands.

Y new mm is rs; (Parser? omce i t: ate mfes'ast me 1 rondnm C mpany.Niagara Falls,"N."Y.-,a eomra'floniof Delaware j v 1 This inventionrelates to improved jointsi'or Application Jane is,- 1947, serial No.755,358 I 1c Claims. (01. 51-183) satisfactory of those now knownbecause of the In making abrasive belts it iscustomary to cut a' stripof suitable dimensions from a web of abrasive coated material comprisinga backing such as paper or cloth havinga layer of abrasive rainsattached to one side by an adhesive. The ends of the strip are thenjoined to form the endless belt or band. In making the splice whichjoins the ends of the strip the abrasive grain is usually removed fromat least one end, a suitable ad- I hesive is applied to the surface fromwhich the from both ends of the strip from which the belt grain has beenremovedand the other end is lapped over the adhesive coated surface,pressed thereon, and the liquid adhesive is then solidified. Anothermethod which is sometimes used is to butt the two ends together andapply a strip of suitable material such as cloth carrying a layer ofadhesive on one side to the back of-the strip and thus fasten the twoendstogether. Abrasive belts made by either of these methods have theobjection that they are thicker at the joint or splice than they are inthe rest of the belt and when the workpiece comes in contact with thisjoint there is a bump which is likely to mar the workpiece. Such a bumpalso puts an undue strain on the joint and as a result the jointsfrequently fail prematurely.

Another method of making belt joints consists in removing substantiallyall of the abrasive grain from both ends of the strip, applying theliquid adhesive to that end which is to be inside the belt, andassembling as described above. In

making such joints one or both of the ends which are to be overlappedmay be tapered as by grinding to form complementary surfaces whichtheoretically should provide a joint of the same thickness as thebacking in the other part of the belt. Actually it is impossible a apractical matter to make joints by this method whichare identical inthickness to the other parts of the backing because of the difliculty ingetting the two ends exactly lined up and because the cement occupiessame space. The tapered or beveled ends are also employed where theabrasive grain is left on that end which is to form the outer surfacebut the same difliculty is there experienced in getting with that to rubover the denuded backing. Except for this difficulty joints of thattype-would be the most fact. that it is possible to assemble the jointunder pressure and to make a joint which is free from the objectionablebump. v

We-have discovered a method of makinga joint of the type where theabrasive grain is removed is made which overcomes the diflicultiespreviously experienced. Briefly stated. our invention comprises the stepof applying over the outer surface of the belt at the joint, andpreferably extending a slight distance into the abrasive grain on eachside of the Joint, a hard tough layer containing a lubricant whichreduces the coefllcient of friction of the layer to such a point that itdoes not wear or become heated in use. In the absence of a lubricant theprotective layer gets unduly warm because of thefriction betweenit andthe workpiece and theheat thus generated has a deleterious efiect on thecement which is used toattach the two ends of the strip and form thejoint or splice.

It is therefore an object of our invention to provide an improvement inabrasive belt joints or splices. Another object is to provide a belt inwhich the joint will be sufliciently strong and wear-resistant so thatit does not fail before the abrasive portion of the belt is worn out.Still another object of the invention is to provide an abrasive beltcomprising a joint which is of such character that it does not bump andyet is strong 'enough to withstand the stresses to which it is rialprepared for assembly in accordance with one modification of ourinvention;

Fig. 2 is similar to Fig. 1 but shows the modification wherein the endsof the backing are tapered;

Fig. 3 is an enlarged side elevation of a joint made from the stripprepared as illustrated in Fig.

Fig. 4 is a top plan view of a completed belt joint made in accordancewith one modification of the invention: and

Fig. 5 is a similar top plan view of a belt joint made according to a.second modification of the invention.

- In carrying out our invention we first provide a strip of abrasivecoated material comprising a backing such as a drill cloth or a lb. ropecylinder paper to one side of which a layer of abrasive f 3 grains isattached by an adhesive such as glue, a suitable varnish, or a syntheticresin. As is well known in the art. abrasive belts are made fromnumerous types of coated abrasive material and it 7 is thereforeunnecessary to provide a detailed dewhich is substantially equal at bothends. We

then apply an adhesive to one of the areas from which the grain has beenremoved, lap the other end over the adhesive coated surface, apply asuspension of a finely powdered solid lubricant such as graphite, talc,mica or molybdenite in-a liquid which is convertible to a tough hardsolid and harden boththe cement and the liquid carrying the lubricant.We usually prefer to complete the joint by hardening the cement whichattaches the two ends before we apply the liquid carrying the lubricantalthough the hardening of the two liquids may be completed in onetreatment.

Referring to the drawings, Fig. 1 shows the two ends of a suitable stripconsisting of a backing I having a layer of abrasive grains 2 attachedto one surface by an adhesive 3. The abrasive grain and adhesive havebeen removed from a portion of each end of the strip as is shown in thedrawings.

In Fig. 2 a backing 4 having the coating of abrasive grains and adhesiveis tapered on each end in a, complementary fashion, the abrasive grainsbeing removed from a portion of each end. The angle of the taper 5 issubstantially the same as that of the taper 6 so that when the adhesiveis applied to surface 5 or 6 or to both surfaces and the ends are buttedthe thickness of the backing at the joint will be closely the same asthat of the other part of the backing 4. At the same time denudedportions are provided above that part of the backing which forms'thejoint.

In Fig. 3 we haveshown a side elevation of an assembled joint made fromthe strip illustrated in Fig. 2 after the ends have been butted and heldtogether by the cement 8 andthe protective layer 1 of hard toughmaterial carrying the lubricant has been applied.

Fig. 4 shows a top plan view of the belt assembled, as for example inaccordance with Fig. 3. In this figure the protective layer 1 extendsonly up to the abrasive grains. Fig. 5 is similar but shows a jointwherein the protective layer 1 has been applied over an area sumcient tocarry it slightly into the abrasive coated portion of each.

and the lower side of the other end. The two ends were then overlapped,clamped together and the Joint was allowed to dry until the glue hadset. V

A coating material to be applied over the exposed outer surface of thejoint was then prepared by first soaking parts by weight of a high gradehide glue in '15 partsby weight of water for minutes and then heating to110150 F.

and stirring until the glue solution was smooth.

25 parts by weight of finely powdered graphite were then stirred intothe 100 parts by weight of glue solution while the solution was held ata temperature of 140-150 F. until the mixture was smooth and. free fromlumps. I

A uniform heavy coating of this mixture was then brushed over the top ofthe splice where the grain had been removed and after the coating hadbeen dried for 24 hours the splices were flexed over a standard beltflexer along the direction of the splice; that is to say, at an angle ofwith the edge of the belt.

The belt thus prepared was used for smoothingsteel and it was found thatthis belt was usable until the abrasive portion of the belt had wornout. Belts made without the protective coating and also belts made witha coating of glue but without graphite failed at the joint long beforethe abrasive portion of the belt was worn out.

Example II A belt was made up exactly according to the procedure ofExample I except that. the coating which was applied over the exposedouter surface 4 of the joint consisted of a glue of Example I withoutany graphite mixed with it and that finely powdered graphite wassprinkled over the glue surface while it was still moist and adhesive.The joint thus formed was found to be fully as satisfactory as that madeaccording to Example I.

I Example III- A strip or Waterproof abrasive cloth made on a backing ofdrill cloth which had been impregnated with a resin to waterproof it andprevent" from a strip approximately'% inch wide from We will nowillustrate our invention by reference to specific examples, it beingunderstood that the examples are not limitative.

Example I A strip of abrasive coat ed cloth comprising a backing ofdrill cloth carrying a coating of each end of the strip and a joint wasmade according to the invention described and claimed in United StatesPatent'No. 2,350,861. Specifically, the end which became the inner sideof the belt was ground to a taper with an abrasive wheel and the underside of the other end of the strip was coated with a plasticizedurea-formaldehyde condensation product made'of the followingcomposition:

, Parts Aqueous solution of urea-formaldehyde resin containing 60%solids Sorbitol ph'thalate 10 Acid catalyst 10 Water 100 to each surfaceby a brush. These surfaces were then dried for a half hour at roomtemperatures and a second coat was appliedand dried for one hour. Thetwo ends were then assembled with the adhesive surfaces in contact andwith the ends aligned to make the belt even and the joint thus formedwas hot pressed at 225 F. under a pressure of 2000 pounds per squareinch for two minutes.

The outer surface of the joint thus formed was then coated with asuspension of finely powdered graphite in the same cement that was usedto form the joint in the proportion of 3 parts of the graphite to 97parts of the solids content of thecement. Two coats of the cementcontaining the graphite were brushed onto the joint to completely coverthe abrasive-free surface and also to extend approximately A; inch overinto the abrasive coated surface on each side of the joint.

After drying, the cement containing the graphite was hot pressed toheat-harden the urea resin whereupon a very smooth and slippery surfacewas provided over the joint.

The belt thus made was mounted on a belt sanding machine provided withmeans for applying water to the workpiece and was tested in this wetoperation. It was found that the joint was still satisfactory when theabrasive portion of the belt had become worn out. On belts madesimilarly except that no protective layer was applied in the one caseand a protective layer of the resin without the graphite was applied ina'secone case the joint failed long before the abrasive portion of thebelt had become useless.

Example IV Example V A belt was made according to the method and usingthe compositions described in Example I except that mica dust wassubstituted for the graphite.

As is shown by the examples, our invention may be practiced in variousembodiments and with various modifications. We have found that the exactamount of lubricant is not critical so long as sufiicient is provided toreduce the friction of the protective layer to the point where it doesnot become heated when the belt is used and yet is not included inproportions sufficient to substantially reduce the hardness andtoughness of the other component of the protective layer such as theglue or the synthetic resin.

As is shown by the examples. the invention is adapted to the productionof abrasive belt joints made from different types of coated abrasivematerials. It may also be used Where the belts are invention may bepracticed without departing ends of the strip, applying a finely dividedlubricant and a liquid which is convertible to a hard tough solid tothat portion of the outer surface of the article which is substantiallydevoid of abrasive grains, and hardening the cement and the saidliquid.

2. A method as claimed in claim 1 wherein the lubricant is powderedgraphite.

3. A method as claimed in claim 1 wherein the liquid applied to theouter surface comprises a suspension of powdered graphite in a solutionof glue.

4. A method as claimed in claim -1 wherein the,

liquid applied to the outer surface comprises a suspension of powderedgraphite in a heat hardenable liquid resinous material.

5. A method as claimed in claim 4 wherein the heat-hardenable liquidresinous material is a urea-formaldehyde condensation product.

6. A method as claimed in claim 4 wherein the heat-hardenable liquidresinous material is a phenol-formaldehyde condensation product.

7. A method as claimed in claim 1 wherein the liquid is applied to theouter surface and the lubricant is applied over the top of the liquidsurface.

8. A method as claimed in claim 1 wherein the cement is first hardenedand the liquid containing the lubricant is applied and hardened thereafter.

9. An abrasive belt comprising a strip of abrasive coated sheet materialprovided with por tions of substantially equal areas at each end whichare substantially devoid of abrasive grains cemented together with theabrasive coated portion forming the outside of the belt, and a layer ofhard tough material comprising a solid lubricant over that portion ofthe outer surface of the belt which is substantially devoid of .abrasiveformaldehyde condensation product.

13. An article as claimed in claim 121 wherein the lubricant isgraphite.

14. An article as claimed in claim 9 wherein the hard tough material isa heat-hardened phenol-formaldehyde resin.

15. An article as claimed in claim 14 wherein the lubricant is graphite.

16. An article as claimed in claim 9 wherein the lubricant is graphite.

' WILLIAM B. SUMMERS.

WILLIAM A. CORSE.

